According to the FBI, the head of LulzSec, known online as Sabu, is really Hector Xavier Monsegur, a 28-year-old father of two from New York. And apparently, as a report from Fox News states, he's been informing on LulzSec since being caught last June.

After the FBI unmasked Monsegur last June, he became a cooperating witness, sources told FoxNews.com.

"They caught him and he was secretly arrested and now works for the FBI," a source close to Sabu told FoxNews.com.

Monsegur pleaded guilty Aug. 15 to 12 hacking-related charges and information documenting his admissions is expected to be unsealed in Southern District Court on Tuesday.

The FBI investigation with which Monsegur assisted has resulted in five further arrests today, as law enforcement officials around the world zeroed in on the remaining leadership of LulzSec. According to the same Fox News report, the five persons charged are:

Ryan Ackroyd ("Kayla"), from London

Jake Davis ("Topiary"), from London

Darren Martyn ("pwnsauce"), from Ireland

Donncha O'Cearrbhail ("palladium"), from Ireland

Jeremy Hammond ("Anarchaos"), from Chicago

The indictment formally charging the five men is expected to be unsealed in court today. The FBI, meanwhile, is reportedly very happy with their work:

"This is devastating to the organization," said an FBI official involved with the investigation. "We're chopping off the head of LulzSec."